Correct modules hierarchy

PumpModule should be on the same level as DripCoffeeModule since they are independent.
So  - this now makes DropCoffeeModule pretty much redundant, since the `@Component` could just include both modules.  As was pointed out earlier, this structure was just to demonstrate.  If you're going to keep this class at all, I would add a comment in the source to the effect that this module exists only to demonstrate aggregating modules, and someone may well not bother to have a separate class, since they can list all the modules on the "modules=" line of the component.